The most difficult problem in manufacturing paint brushes is the fastening of the bristles. On the one hand, it is necessary that a sufficiently large number of bristles can be fixed to obtain the desired density of the bundles of bristles formed from the bristles. On the other hand, it must be ensured that the bristles are reliably fixed so that they do not fall out when used.
One kind of fastening consists in inserting the bristles into a sleeve as a compact bundle and to glue the ends of the bristles arranged in the sleeve together, for example by using a synthetic resin. The handle of the paint brush is then connected with the sleeve. Though a very compact bundle of bristles can be obtained with this kind of fastening, the individual bristles are not held in a particularly reliable manner. Another kind of fastening consists in attaching the bristles in holes, for example in a wooden body, using small clamps. Though it is in principle possible that the bristles are comparatively well fixed with this kind of fastening, the holes used to receive the bristles must have a comparatively large distance from each other as otherwise, the body containing the holes does not have a sufficient stability to hold the clamps. The required distance of the holes from each other leads to the fact that the bundle of bristles is not particularly compact. This problem is even more serious if natural bristles are used, for example bristles of hog hair. For example, whereas in synthetic bristles the clamp can be arranged in the center of the bristles curved in a U-shaped and both ends of the bristle can be used, only one end can be used in the case of bristles of hog hair, more specifically the end opposite to the root of the hair. As a result, the bristles must be configured to be longer than the actual bundle of bristles, as the end portion placed inside the paint brush is bent to be adapted to be fixed with the clamp. This is disadvantageous with regard to cost, as natural bristles are particularly expensive. Furthermore, a very low compactness of the bundle of bristles is obtained.
A paint brush should have low manufacturing costs, a compact bundle of bristles, and a reliable fastening of the individual bristles.